New cars

ABSTRACT

THIS IS A METHOD FOR AUTOMATICALLY ESTIMATING THE NUMBER OF VEHICLES PRESENT ON A SECTION OF ROADWAY FROM MEASUREMENT OF SPEED AND VEHICLE FLOW AT THE ENTRANCE AND EXIT POINTS OF THE ROADWAY SECTION. THE METHOD COMPRISES THE STEPS OF COMPUTING ROUGH COUNT ESTIMATES OF THE NUMBER OF VEHICLES IN SAID ROADWAY AT REGULAR INTERVALS REFERRED TO AS OBSERVATION PERIODS, AND THEN CORRECTING THESE ESTIMATES BY A SEQUENTIAL CORRECTION SCHEME WHICH FILTERS OUT RANDOM ERRORS PRESENT IN THE COUNT. AT BOTH THE ENTRANCE AND EXIT POINTS OF THE ROADWAY, DETECTOR MECHANISMS MONITOR THE NUMBER OF PASSING VEHICLES AND THEIR RESPECTIVE VELOCITIES. FOR EACH OBSERVATION PERIOD, THE INPUT AND OUTPUT VELOCITIES ARE AVERAGED AND AN ESTIMATE OF TRAVEL TIME OVER THE ROADWAY IS COMPUTED. THEN, A ROUGH ESTIMATE OF THE NUMBER OF VEHICLES IN THE ROADWAY IS COMPUTED FROM AN INVENTORY OF VEHICLE ARRIVALS AT THE INPUT OF SAID ROASDWAY AND THE TRAVEL TIME OF EXITING VEHICLES. THE ROUGH ESTIMATE IS THEN ADJUSTED BY MEANS OF SEQUENTIAL ESTIMATOR WHICH UTILIZES THE REQUIREMENT THAT THE COUNT OBTAINED AT THE END OF TWO SUCCESSIVE OBSERVATION PERIODS IS EQUAL TO THE NUMBER OF CARS PRESENT IN THE ROADWAY AT THE PRIOR OBSERVATION PERIOD PLUS THE DIFFERENCE BETWEEN THE NUMBER OF VEHICLES ENTERING AND EXITING THE ROADWAY DURING THE PRESENT OBSERVATION.

DEFENSIVE PUBLTGATTQN UNITED STATES PATENT OFFICE Published at the request of the applicant or owner in accordance with the Notice of Dec. 16, 1969, 869 0.G. 687. The abstracts of Defensive Publication applications are identified by distinctly numbered series and are arranged chronologically. The heading of each abstract indicates the number of pages of specification, including claims and sheets of drawings contained in the application as originally filed. The files of these applications are available to the public for inspectionand reproduction may be purchased for 30 cents a sheet.

Defensive Publication applications have not been examined as to the merits of alleged invention. The Patent Ofiice-makes no assertion as to the novelty of the disclosed subject matter.

PUBLISHED MARCH 5, 1974 Int. Cl. G061? 15/48 U.S. CI. 444-1 5 Sheets Drawing. 32 Pages Specification ON LINE SEQUENTIAL ESTIMATION OF TRAFFIC FLOW DENSITY MEASURED DATA INPUT ENTRANCE VELOOITY AND FLOII IIEASUREIIENTS \30 EXIT- VELOCITY AND FLOW MEASUREMENTS OOHPUTE SNOOTHEO ENTRANCE VELOCITY \32 AND SNOOTIIED EXIT VELOCITY IS THIS THE FIRST OBSERVATION PERIOD 3T INITIALIZE FILTER AIIO ESTIMATES UPDATE ESTIMATES USING FILTER EIIUATIONS This is a method for automatically estimating the number of vehicles present on a section of roadway from measurements of speed and vehicle flow at the entrance and exit points of the roadway section. The method comprises the steps of computing rough count estimates of the number of vehicles in said roadway at regular intervals, referred to as observation periods, and then correcting these estimates by a sequential correction scheme which filters out random errors present in the count.

At both the entrance and exit points of the roadway, detector mechanisms monitor the number of passing vehicles and their respective velocities. For each observation period, the input and output velocities are averaged and an estimate of travel time over the roadway is computed. Then, a rough estimate of the number of vehicles in the roadway is computed from an inventory of vehicle arrivals at the input of said roadway and the travel time of exiting vehicles. The rough estimate is then adjusted by means of sequential estimator which utilizes the requirement that the count obtained at the end of two successive observation periods is equal to the number of cars present in the roadway at the prior observation period plus the difference between the number of vehicles entering and exiting the roadway during the present observation.

March 5, 1974 c ls ETAL T920,013

METHOD FOR ON-LINE ESTIMATION OF TRAFFIC DENSITY 5 Sheets-Sheet 1 Original Filed Sept. 14, 1971 TYPICAL VEHICLE TRAJECTORIES IN THE SPACE-TIME PLANE FIG. 2

NORMALIZED AUTOCORRELATION FUNCTIONS OF ERRORS IN THE ROUGH COUNTS OF VEHICLES T (SEQ) INVENTORS DENOS C. GAZIS CHARLES H. KNAPP ATTORNEY March 5, 1974 c, GAZls ETAL T920,013

METHOD FOR ON-LINE ESTIMATION OF TRAFFIC DENSITY Original Filed Sept. 14, 1971 5 Sheets-Sheet 3 INPUT SPEED OUTPUT SPEED INPUT. OUTPUT MEASUREMENTS MEASUREMENTS FLOW FLOW 10\ RUNNING AVERAGE SPEED RUNNING COUNT -12 PROCESSOR PROCESSOR k k k k I I I I STORAGE OF INPUT/OUTPUT STORAGE OF INPUT/OUTPUT \16 SPEED AVERAGE COUNT CHANGE 18 TRAVEL TIME COMPUTER L D v k-I k I A k-I D g- SEQUENTIAL ESTIMATOR D 26. 0

[III I SEQUENTIAL ESTIMATE March 5, 1974 D. c. GAZIS ETAL METHOD FOR ONLINE ESTIMATION OF TRAFFIC DENSITY Original Filed Sept. 14, 1971 FIG. 4 ON LINE SEQUENTIAL ESTIMATION OF TRAFFIC FLOW DENSITY MEASURED DATA INPUT 5 Sheets-Sheet 5 ENTRANCE VELOCITY AND FLOIY MEASUREMENTS EXIT VELOCITY AND FLOW MEASUREMENTS COMPUTE SMOOTHED ENTRANCE-VELOCITY AND SMOOTHED EXIT VELOCITY COMPUTE TRAVEL TIME COMPUTE ROUGH COUNT IS nus THE FIRST OBSERVATION PERIOD INITIALIZE FILTER AND ESTIMATES UPDATE ESTIMATES USING FILTER EQUATIONS March 5, 1 974 D. C. GAZlS ETAL Original Filed Sept.

INPUT 5 Sheets-Sheet L (SMOOTHED VELOCITY MEASUREMENTS) 5 INITIALIZEA,LT -40 COMPUTE TRAVEL TIME sn KL=0 42 COMPUTE A 5 s 1 I 7 b 12[V (k-LT) V (k) V (k) Vg(k-LT)] 1[ 1. I I 1- c- 12 V (k-LT) V (k) V (k-LT)V (k) V (k)V (kLT) COMPUTE TRAVEL TIME (k) coMPuTE TRAVEL TIME (k) =D|STANCE -0 =TIIsTAIIcE 2 4 2 IS I (TRAVEL TIME (k) (A-3) 49 OR TRAVEL TIME(k) (A+7)) AND KL 2? SET LT=FLO0R OUTPUT (TRAVEL TIME(k)/5) (TRAVEL TIME (k)) A=(5)-(LT), KL KL+1 March 5, 1974 c, GAZIS ETAL T920,013

METHOD FOR ON-LINE ESTIMATION OF TRAFFIC DENSITY Original Filed Sept. 14, 1971 5 Sheets-Sheet s F I G. 6 COMPUTE ROUGH COUNT INPUT (TRAVEL TIME (k) NEW CARS (k) COHPUTE KT FLOOR TRAVEL TIME (k)/5 51 COUNT (k) NEW CARS (kKT) [TRAVEL TIME (k)/5KT] COMPUTE k- KT 1 52 COMPUTE r courn (k) coum (k) NEW CARS (J) 54 YES NO OUTPUT (COUNT (k)) 

